Wear observations applied to Lifeboat Slipway Launches.

Abstract

It is necessary to use an inclined slipway to launch a large lifeboat in locations where there is no natural harbour or where there is a large tidal range. Slipway stations consist of an initial section where the boat is held on rollers followed by an inclined keelway of nickel/chromium coated steel, the lifeboat is released from the top of the slipway and proceeds under its own weight into the water. The lifeboat is subsequently recovered to the top of the slipway using a winch line. With the introduction of the new, larger Tamar class lifeboat existing boathouses are being upgraded and existing low friction coated steel slipway lining materials replaced with a low-friction jute fibre/phenolic resin composite, which is designed to operate with unlubricated conditions. This has led to problems of high wear on slipway panels, particularly where the lifeboat mounts the slipway for recovery. This paper describes a method for assessing slipway lining materials and lubricants. The selection of an appropriate test machine, the TE92 rotary tribometer, and design of a modified ring on disc arrangement incorporating panel interfaces and attaching holes effects is described. An experimental methodology is developed using programmed running intervals to simulate dwell effects. Experimental data is thus presented to establish slipway panel wear rates for a range of lubricants and contact pressures. Experimental results are incorporated into real-world slipway surveys to develop the wear scenario. Results and implications of this research for future lifeboat slipway design are discussed.